Memory traces and representation

Phenomenology and the Cognitive Sciences -     

Memory for position and

Memory for the position of an object is biased. When asked to judge whether an object has changed its position with respect to a position shown a few milliseconds before, observers tend to detect the displacement more often when the displacement is not in the expected direction (downward for a falling object). The hypothesis proposed by Freyd (1983, 1987) states that the internal representation of an object is intrinsically dynamic. Therefore, the forces perceived as acting on the object affect the representation. Quantitative predictions of this model were tested in three experiments by measuring memory distortion for the position of an object on an inclined plane. Angle of inclination and retention interval were varied. The results for different inclinations support the physical model. The time course of the memory distortion suggests a new view about the relation between this phenomenon and very short-term memory.     

Memory search and the neural representation of context

A challenge for theories of episodic memory is to determine how we focus memory search on a set of recently learned items. Cognitive theories suggest that the recall of an item representation is driven by an internally maintained context representation that integrates incoming information with a long time-scale. Neural investigations have shown that recalling an item revives the pattern of brain activity present during its study. To link these neural and cognitive approaches, we propose a framework in which context is maintained and updated in prefrontal cortex, and is associated with item information through hippocampal projections. The proposed framework is broadly consistent with neurobiological studies of temporal integration and with studies of memory deficits in individuals with prefrontal damage.     

Both-edges representation of letter position in reading

The representations that underlie our ability to read must encode not only the identities of the letters in a word, but also their relative positions. In recent years, many new proposals have been advanced concerning the representation of letter position in reading, but the available data do not distinguish among the competing proposals; multiple theories, each positing a different letter position representation scheme, are compatible with the evidence. In this article, we report two experiments that used the illusory word paradigm (e.g., Davis & Bowers, Journal of Experimental Psychology: Human Perception and Performance, 30: 923–941, 2004) to distinguish among alternative schemes for representing letter position in reading. The results support a scheme that uses both the beginning and the end of a word as anchoring points. This both-edges scheme has been implicated in letter position representation in spelling (Fischer-Baum, McCloskey, & Rapp, Cognition, 115: 466–490, 2010), as well as in position representation in verbal working memory (Henson, Memory & Cognition, 27: 915–927, 1999), suggesting that it may be a domain-general scheme for representing position in a sequence.     

Memory as a cognitive representation of post-traumatic growth

Background and objectives: Previous studies on traumatic memory have primarily focused on the correlation between traumatic symptoms and negative memories, often utilizing the directed forgetting paradigm. Different from previous research, this study aimed to examine the correlation of post-traumatic growth (PTG) and positive memories, with the objective to explore the directed forgetting effect of positive material and its relationship with PTG.

Design: A 2 (PTG level: high vs. low)?×?2 (instructions: To-Be-Forgotten vs. To-Be-Remembered)?×?3 (word valence: positive vs. neutral vs. trauma related) mixed-factorial-designed experiment was applied.

Methods: Participants were 46 senior high-school students who had survived in the Sichuan earthquake in 2008. Participants were divided into two groups based on PTG: high (n?=?24) and low (n?=?22). Both groups were presented, and asked to recall, three word categories (positive, trauma-related, and neutral) following the directed forgetting paradigm.

Results: A mixed-design factorial ANOVA yielded a significant interaction effect of word valence and PTG group, with the high-PTG group recalling more positive words than the low-PTG group.

Conclusions: This was the first study to identify a key cognitive process of PTG by integrating the directed forgetting paradigm into an investigation of PTG.     

Recognition memory retention interval and information load

Two experiments were conducted to study the effect of retention interval and information load on short-term recognition memory in retarded subjects. The task consisted of an input trial of 1–15 pictures followed by a test trial of one picture, with the subject having to press different levers to indicate whether the probe picture had been present on the input trial. Retention intervals between input trial and test trial were manipulated over a range of 1–24 sec. Both accuracy and latency of response were measured. Results showed that latency increased and accuracy decreased as a function of both retention interval and number of stimuli. In addition, number of stimuli interacted with retention interval such that accuracy was not affected by retention interval when information input was small, but decreased quite dramatically at longer retention intervals when input was larger. The results were discussed in terms of current memory search models for both normal and retarded subjects.     

Memory for numbers: Nominal vs. magnitude information

Across three paired associate learning experiments, the recall of four-digit number responses to word stimuli favored the most significant digit over the least significant (magnitude encoding rather than exhibiting typical bowed serial position functions (nominal encoding). Only with instructions emphasizing exact recall of each individual digit did recall functions revert to bowed curves. The results are interpreted as evidence for two kinds of number coding in semantic memory.     

Serial position phenomena: Memory for acts, contents and spatial position patterns

The influence of functional control operations on serial position effects was examined in a series of four experiments. When recall was required of performed operations as well as of the information operated upon, the result generally turned out to be absence of recency effects and presence of primacy effects. Primacy effects were found to be more prominent with active execution of operations than with passive list reception. Simultaneous presence of spatial and temporal position cues was shown to coincide with disruption of the ordinary primacy-recency pattern. The findings were taken to prove the importance of functional factors, and were interpreted as in agreement with a two-stage analysis of serial learning where the first stage is assumed to involve the differentiation of list items and the second stage the integration of differentiated items. The experiments were claimed to indicate that memory is better understood from a problem-solving than from an information-processing point of view.     

Memory for information about individuals

A semantic network model is structured so that usually there is only one node in the network to represent each individual. A series of experiments were performed to determine under what circumstances subjects would show unitary memory for individuals. The experiments were principally concerned with the speed with which subjects could retrieve the facts and make inferences from them. Subjects learned facts about individuals which could be referred to by two labels. The semantic network model predicted that subjects would integrate facts learned to one label with facts learned to the other. Evidence for such integration was found, but only when considerable effort was taken to encourage the subjects to develop a unitary impression of the individual. The situation was also investigated in which the subjects did not learn of the identity between the two labels until after the facts were learned to each label individually. There was evidence that subjects set up two nodes to represent the. individual, one for each label. There was also evidence that, upon learning of the identity, subjects chose to abandon one of the two nodes and to start a process of copying information from the to-be-abandoned node to the preserved node.     

Memory for multidimensional source information

Source memory may comprise recollection of multiple features of the encoding episode. To analyze the simultaneous representation and retrieval of those multiple features, a multinomial memory model is presented that measures memory for crossed dimensions of source information. The first experiment investigated the validity of the new model. The model showed an excellent statistical fit to empirical data, and the parameters of multidimensional source memory were sensitive to manipulations of source similarity on distinct dimensions. The second experiment used the model to test the hypothesis that source memory for individual context attributes is stochastically related in the case of conscious recollection but independent in the case of familiarity-based recognition judgments. The prediction was supported by the introduction of a "remember"-"know" distinction in a multidimensional source memory test.     

Memory for object position in natural scenes

Memory for the positions of objects in natural scenes was investigated. Participants viewed an image of a real-world scene (preview scene), followed by a target object in isolation (target probe), followed by a blank screen with a mouse cursor. Participants estimated the position of the target using the mouse. Three conditions were compared. In the target present preview condition, the target object was present in the scene preview. In the target absent preview condition, the target object not present in the scene preview. In the no preview condition, no preview scene was displayed. Localization accuracy in the target present preview condition was reliably higher than that in the target absent preview condition, which was reliably higher than localization accuracy in the no preview condition. These data demonstrate that participants can remember both the spatial context of a scene and the specific positions of local objects.     

The representation of spatial information in memory

Following memorisation of the spatial arrangement of an array of circles, subjects were asked to recall the circles in a type of free-recall task designed to determine the structure of the memorised information. Their performance showed that the circles tended to be recalled in an order that corresponded with a top-to-bottom ordering of circles on the array. In a second experiment the input order of the circles was varied by presenting them successively. The results indicated that input order influenced recall order. The implications for hypotheses about the structure and manipulation of stored spatial information were discussed.     

How tool use and arm position affect peripersonal space representation

Experiment 1 investigated whether tool use can expand the peripersonal space into the very far extrapersonal space. Healthy participants performed line bisection in peripersonal and extrapersonal space using wooden sticks up to a maximum of 240 cm. Participants misbisected to the left of the true midpoint, both for lines presented in peripersonal and for those presented in extrapersonal space, confirming a peripersonal space expansion up to a distance of 240 cm. Experiment 2 investigated whether arm position could influence the perception of peripersonal and extrapersonal space during tool use. Participants performed line bisection in the peripersonal and in the extrapersonal space (up to a maximum of 120 cm) using wooden sticks in two different conditions: either with the arm bent or with the arm stretched. Results showed stronger pseudoneglect in the stretched arm condition.     

Tune recognition with reduced pitch and interval information

Twenty subjects were tested on their ability to recognize simple tunes from which rhythm information had been removed. Only the first phrase of each tune was presented. The purpose of the experiment was (a) to determine whether stimuli containing only high harmonics can evoke a sense of musical pitch, and (b) to provide a set of data in normal subjects with which the performance of deaf subjects whose auditory nerve is stimulated electrically can be compared. Each subject was tested on five sets of stimuli presented in a counterbalanced order. These stimuli were (I) pulse trains high-pass filtered at 2 kHz, with repetition rates in the range of 100-200 p.p.s.; (2) as in (I) but high-pass filtered at 4 kHz; (3) sinusoids with musical intervals compressed, so that the “octave” was a ratio of I:I·3; (4) sinusoids with the musical intervals expanded, so that the “octave” was a ratio of I:4; (5) sinusoids of a constant frequency in which the normal frequency changes were translated into intensity changes, each semitone being represented by a 3 dB change in level. The results indicate that a pattern of intensity changes does not support tune recognition, and that, although the pitch contour alone allows reasonable performance, subjects do use musical interval information in recognizing tunes. Stimuli containing only high harmonics can provide such interval information, and thus can evoke a sense of musical pitch. Preliminary results from a deaf subject stimulated electrically with an electrode on the surface of the cochlea indicate that such stimulation can also evoke a sense of musical pitch. It is concluded that musical pitch information can be carried in the time-pattern of nerve impulses in the auditory nerve.